drm/amd/display: invalid parameter check in dmub_hpd_callback

commit 978ffac878fd64039f95798b15b430032d2d89d5 upstream.

The function performs a check on the "adev" input parameter, however, it
is used before the check.

Initialize the "dev" variable after the sanity check to avoid a possible
NULL pointer dereference.

Fixes: e27c41d5b0681 ("drm/amd/display: Support for DMUB HPD interrupt handling")
Addresses-Coverity-ID: 1493909 ("Null pointer dereference")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 2b5e8de..5323d00 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -653,7 +653,7 @@ void dmub_hpd_callback(struct amdgpu_device *adev, struct dmub_notification *not
        struct drm_connector_list_iter iter;
        struct dc_link *link;
        uint8_t link_index = 0;
-       struct drm_device *dev = adev->dm.ddev;
+       struct drm_device *dev;
 
        if (adev == NULL)
                return;
@@ -670,6 +670,7 @@ void dmub_hpd_callback(struct amdgpu_device *adev, struct dmub_notification *not
 
        link_index = notify->link_index;
        link = adev->dm.dc->links[link_index];
+       dev = adev->dm.ddev;
 
        drm_connector_list_iter_begin(dev, &iter);
        drm_for_each_connector_iter(connector, &iter) {